Raspberry Pi 4 WiFi stops working at 2560x1440 screen resolution

One of the micro HDMI cables that we used
One of the micro HDMI cables that we used

This is part of a series of posts on the design and technical steps of creating Himblick, a digital signage box based on the Raspberry Pi 4.


This post seem to have become quite popular, so to be clear, the intention is to document the issue that we spent a whole day chasing so that others won't have to.

It's been fantastic to see how this has made the rounds and resulted in actual RF measurements being made, and better pinpointing of the issue than we could ever have achieved.

I greatly admire Raspberry Pi's work. Thanks to them we get to have an affordable standard platform with a wide use base, which over time gets extremely well known, and as such can be a very well mapped ground to build on.

Original post

One full day of crazy debugging, and the result is that if the Raspberry Pi 4 outputs HDMI at a resolution of 2560x1440, the WiFi stops working.

Any lower resolution we tried, from 2048x1080 down, does not show this problem.

We did not try any resolution above 2560x1440, for lack of a monitor that would do it.

We reproduced this:

At the bottom of this forum thread (guestxyz dated Aug 07) someone mentioned screen resolution, which is what finally prompted us to try that. Thanks, guestxyz!

After confirming what the trigger was that caused the problem and chatting about it on IRC, olasd found this forum thread where more people are experiencing similar issues.

Further things left to try after chatting about it on IRC: